Sintered alloy is produced in a process in which alloy powder is combined and blended, filled into a mould, press-formed, and then sintered in a determined atmosphere and at a determined temperature. According to such sintering method, metals and alloys which are hardly obtained by usual melting and casting method, can be easily produced, and a plurality of functions can be easily obtained together, which enables to produce parts having peculiar function or functions. Also, sintered alloy is adapted for production of porous materials, hard-machining materials and complicated mechanical parts. In recent years, such sintered alloy has been used for valve seats for which high abrasion resistance is required.
Concerning sintered alloys used for valve seats, there was seen Japanese Publication Gazette No.51-13093/1976 of which the entire disclosure is expressly incorporated herein by reference, which discloses an iron series sintered alloy used for valve seats having a high abrasion resistance as well as a heat resisting, anti-corrosion property even under usage of leadless gasoline. This sintered alloy includes a lot of C, Ni, Cr, Mo,Co and W,and also ferromolybdenum particles and special alloy particles consisted of C-Cr-W-Co dispersed in pearitic structure, these particles being accompanied with Cu and Ni dispersed therearound. For such reasons, this sintered alloy needs in particular a lot of W and Co annexed thereto in order to effect the characteristics of high heat resistance, abrasion resistance, anti-corrosion, etc. Therefore, the valve seats made of this sintered alloy will be expensive and thus accompanied with drawbacks at cost.